The intensive introduction of advanced composites in primary structures has become a fundamental process of structural optimization (based on weight savings and the improvement of mechanical properties), one of the top priorities in the design and manufacture of a new generation of aircrafts. The introduction of an effective structural monitoring system capable of predicting the failure of load paths in a structure designed according to damage tolerance criteria would allow optimizing its design and, accordingly, reducing its weight.
Optical fiber sensors can be effectively used to measure thermomechanical deformation and even to detect damage events operating both alone in passive structural monitoring systems and in combination with other devices, forming an active monitoring system. One of their main advantages is their capacity to be embedded in composite structures, being intimately integrated into the structures.
However, one of the drawbacks of this integration is the difficulty that the integration of the optical fiber has under real laminate manufacturing conditions and the repair of these same fibers once they are embedded. Optical fiber has extremely small dimensions and due to its fragility, it is difficult to handle during the handling operations associated to the integration processes during the manufacture of the laminate, the manufacture of the vacuum bag and curing in the autoclave (or any other alternative laminate consolidation process), the connectorization and subsequent maintenance and/or repair operations of the same optical fiber of the housing laminate. In particular, the scarce possibilities of accessing the optical fiber once it is embedded are very slim and even slimmer yet with regard to its successful repair, which is incompatible with the reparability requirements needed when the structural health and maintenance criteria are bound to the correct working of the network of sensors integrated in the structure.
The present invention is aimed at solving this drawback.